Using the RandR-enabled nvidia 302.xx beta driver in 12.04 with a realtime kernel

Warning

The patch in this question is for kernel 3.4, and so is the one below; a realtime-patched kernel 3.4 is required.

The new nvidia 302 driver requires the video ABI that xorg-server 1.12 provides, and unfortunately Precise comes with xorg-server 1.11. The following instructions involve adding the xorg-edgers PPA as a software source to provide xorg-server 1.12, and this poses a certain risk of breakage. The uninstallation instructions are at the bottom, but read them through for possible hiccups there.

Instructions

Modifying the packaged nvidia driver

Create a temporary directory and change into it with: 

mkdir -p ~/tmp/nvidia_302_fixrt && cd ~/tmp/nvidia_302_fixrt

Download the nvidia-current_302*.deb from the xorg-edgers PPA by browsing the packages for Precise under nvidia-graphics-driver_302* here. At the moment of this writing, a direct download can be performed with:
```
wget https://launchpad.net/~xorg-edgers/+archive/ppa/+files/nvidia-current_302.17-0ubuntu1~xedgers~precise1_amd64.deb
```

Extract the .deb with:

dpkg-deb -x nvidia-current_*.deb deb_contents && dpkg-deb --control nvidia-current_*.deb deb_contents/DEBIAN

Add the patch to the deb_contents/usr/src/nvidia-current*/patches directory by pasting the following in a terminal:

d=$(echo deb_contents/usr/src/nvidia-current*/patches) ; cat > $d/buildfix_kernel_rt_3.4.patch <<'EOF'
diff -u a/conftest.sh b/conftest.sh
--- a/conftest.sh       2012-05-03 09:49:19.582854050 +0100
+++ b/conftest.sh       2012-05-03 09:52:58.524101586 +0100
@@ -95,7 +95,7 @@
         fi
     fi

-    CFLAGS="$CFLAGS $OUTPUT_CFLAGS -I$HEADERS $AUTOCONF_CFLAGS"
+    CFLAGS="$CFLAGS $OUTPUT_CFLAGS -I$HEADERS -I$OUTPUT/arch/x86/include/generated $AUTOCONF_CFLAGS"

     test_xen

@@ -965,11 +965,12 @@
             #
             echo "$CONFTEST_PREAMBLE
             #include <linux/acpi.h>
+            #include <acpi/acpixf.h>
             void conftest_acpi_walk_namespace(void) {
                 acpi_walk_namespace();
             }" > conftest$$.c

-            $CC $CFLAGS -c conftest$$.c > /dev/null 2>&1
+            #CC $CFLAGS -c conftest$$.c > /dev/null 2>&1
             rm -f conftest$$.c

             if [ -f conftest$$.o ]; then
@@ -980,6 +981,7 @@

             echo "$CONFTEST_PREAMBLE
             #include <linux/acpi.h>
+            #include <acpi/acpixf.h>
             void conftest_acpi_walk_namespace(void) {
                 acpi_walk_namespace(0, NULL, 0, NULL, NULL, NULL, NULL);
             }" > conftest$$.c
@@ -1604,6 +1606,9 @@
             fi
         fi

+        RET=0
+        SELECTED_MAKEFILE=Makefile.kbuild
+
         if [ "$RET" = "0" ]; then
             ln -s $SELECTED_MAKEFILE Makefile
             exit 0
diff -u a/nv-linux.h b/nv-linux.h
--- a/nv-linux.h        2012-05-03 09:49:19.622853547 +0100
+++ b/nv-linux.h        2012-05-03 09:56:12.045668690 +0100
@@ -291,7 +291,18 @@
 #endif
 #endif

-#if defined(CONFIG_PREEMPT_RT)
+#if defined(CONFIG_PREEMPT_RT_FULL)
+typedef raw_spinlock_t            nv_spinlock_t;
+#define NV_SPIN_LOCK_INIT(lock)   raw_spin_lock_init(lock)
+#define NV_SPIN_LOCK_IRQ(lock)    raw_spin_lock_irq(lock)
+#define NV_SPIN_UNLOCK_IRQ(lock)  raw_spin_unlock_irq(lock)
+#define NV_SPIN_LOCK_IRQSAVE(lock,flags) raw_spin_lock_irqsave(lock,flags)
+#define NV_SPIN_UNLOCK_IRQRESTORE(lock,flags) \
+   raw_spin_unlock_irqrestore(lock,flags)
+#define NV_SPIN_LOCK(lock)        raw_spin_lock(lock)
+#define NV_SPIN_UNLOCK(lock)      raw_spin_unlock(lock)
+#define NV_SPIN_UNLOCK_WAIT(lock) raw_spin_unlock_wait(lock)
+#elif defined(CONFIG_PREEMPT_RT)
 typedef atomic_spinlock_t         nv_spinlock_t;
 #define NV_SPIN_LOCK_INIT(lock)   atomic_spin_lock_init(lock)
 #define NV_SPIN_LOCK_IRQ(lock)    atomic_spin_lock_irq(lock)
@@ -954,7 +965,9 @@
     return ret;
 }

-#if defined(CONFIG_PREEMPT_RT)
+#if defined(CONFIG_PREEMPT_RT_FULL)
+#define NV_INIT_MUTEX(mutex) sema_init(mutex,1)
+#elif defined(CONFIG_PREEMPT_RT)
 #define NV_INIT_MUTEX(mutex) semaphore_init(mutex)
 #else
 #if !defined(__SEMAPHORE_INITIALIZER) && defined(__COMPAT_SEMAPHORE_INITIALIZER)
EOF

Add the patch to dkms.conf by pasting this in a terminal:

d=$(echo deb_contents/usr/src/nvidia-current*) ; cat >> $d/dkms.conf <<'EOF'
PATCH_MATCH[1]="^3\.4.*(rt|realtime)"
PATCH[1]="buildfix_kernel_rt_3.4.patch"
EOF

Modify the version number in deb_contents/DEBIAN/control by issuing:

 sed -i 's/^\(Version: .*\)$/\1+rtfix/' deb_contents/DEBIAN/control

Repackage the driver with:

 dpkg -b deb_contents nvidia-current_$(sed -n 's/^\(Version: *\)//p' deb_contents/DEBIAN/control)_amd64.deb

Installing the PPA and the modified driver

Add the xorg-edgers PPA:

 sudo add-apt-repository ppa:xorg-edgers/ppa && sudo apt-get update && sudo apt-get dist-upgrade

Install the locally-modified .deb with: 

sudo dpkg -i nvidia-current_*+rtfix_*.deb

Keeping up to date

The xorg-edgers PPA will update with newer versions of the nvidia driver as they come out; you will need to repeat the re-packaging instructions above with each new release.

Uninstalling

You should be able to revert to the nouveau driver with the following:

    sudo apt-get remove nvidia-current
    sudo apt-get install ppa-purge
    sudo ppa-purge ppa:xorg-edgers/ppa

In my case, this process involved uninstalling wine along with some i386 packages (which should have been downgraded instead). Be wary of ppa-purge if you are on amd64 since it does not get along well with multiarch (as indicated in the PPA warnings); in my case the outcome was a non-issue (I simply reinstalled wine), but other people might end up with badly broken dependencies depending on what they have installed.